Employee Dishonesty Claim - Insurance

Hello,

We have an Employee Dishonesty claim to make against our insurance company for a fraud case involving our (now former) employees. There are about 15 individuals who committed fraud against us, but the insurance company is grouping up the incidents as one occurrence and only willing to submit payment for only one occurrence. We believe that each case should be treated as own and not grouped together, as the employees were not working together, but worked alone and in different times / locations to obtain personal benefits at the cost of the company. Our insurance company is fighting back on this stating that this is on their policy:

d. All loss or damage:

(1) Caused by one or more persons; or
(2) Involving a single act or series of acts;
is considered one occurrence.

Our question is, how is it even determined whether something is considered one occurrence or not? The language is very unclear and vague and could possibly mean anything can be grouped under one occurrence. We would like to see is there's a possibility of fighting this and winning the case if we were to take legal action and hire a lawyer.

Thank you!